21. Many teenagers feel lonely, _______ no one understands them and the changes they are going through.

   A. so that          B. in case        C. even if              D. as if

22. Lei Feng is always ready to help others when they are in trouble and he never _________ their request.

   A. turns up       B. turns over   C. turns in          D. turns down

23. –Do you have anything to say for yourselves?

   –Yes, there’s one point __________ we must insist on.

   A. why               B. where             C. how                D. /